The present invention relates in general to semiconductor devices and, more particularly, to semiconductor device packaging systems.
The complexity of modern integrated circuits and other environmentally sensitive devices has increased their susceptibility to damage from environmental factors. As a result, most devices are transported from the factory to a customer in packages that minimize handling damage and damage from electrostatic discharge (ESD) and humidity. In a typical packaging system, devices are mounted on a carrier tape which is wound on a reel and held in place with a strip of masking tape attached to the leader of the carrier tape. The reel assembly is shipped in a conductive aluminized bag to prevent high electrostatic potentials from building up across pins of the integrated circuits and damaging internal components. Humidity is controlled by drawing a vacuum in the aluminized bag and sealing the bag to prevent moisture from entering.
Residual moisture within the aluminized bag is controlled by a granular or powdered desiccant such as silica gel, which is placed in a nylon bag and inserted in the aluminized bag with the reel assembly prior to vacuum sealing. The desiccant bags are placed in strategic locations within the aluminized bag to limit damage. Placement is often performed manually, which is time consuming and expensive. For example, in some packaging systems, the desiccant bag is placed over the reel assembly and held in place by the vacuum seal. A problem with such systems is that the desiccant bag creates a bulge in the aluminized bag which creates uneven pressure on the reel assembly. During shipment, the uneven pressure can deform the reel and damage the integrated circuit leads.
In other packaging systems, desiccant bags are placed in corners of the aluminized package, which allows the reels to be stacked without becoming deformed. However, when a vacuum is created and the sides of the aluminized bag collapse, the desiccant bags can become sealed off from the reel assembly, effectively creating a vapor barrier that prevents moisture from being drawn away from the devices.
Aluminized bags are opaque, so that identifying the devices within the bag requires opening the bag and releasing the vacuum. Providing view windows in the aluminized bags increases cost and increases the potential for leakage at the seam of the view window.
Hence, there is a need for a packaging system for semiconductor devices which more reliably provides both ESD and humidity protection while protecting the leads of the semiconductor device from being deformed or damaged.